9:30 p.m summary:

A Fairfax fire department spokesman says two people, one of them a child, are dead after they were swept away in rain-swollen waters Thursday night.

Dan Schmidt, spokesman for Fairfax County Fire and Rescue, says a child died after being swept away in the Piney Branch Creek in Vienna.

He also said another person had died in a similar incident, but did not know in what body of water. Other details were not available. However, earlier in the evening Fairfax officials said a 12-year child had fallen into badly swollen Piney Branch Creek in Vienna near Marcliff Court.

“We have first responders, both firefighters and police, and they are on the scene,” said Merni Fitzgerald, a spokeswoman for Fairfax County.

The Northern Virginia area, especially the southern region, was hit hard by rising floodwaters. Several schools and offices canceled events on Thursday and Friday. A flash flood warning was extended to late tonight and early tomorrow morning in cities and counties around the D.C. region.

Fairfax County police and fire officials successfully retrieved 12 motorists stranded in high-water in the southern part of the county, but dispatchers continued to field numerous calls for swift-water rescues, according to police radio reports.

Shortly after 9 p.m., police began responding to a report of vehicles stranded in “rising water” on Telegraph Road near the Fairfax County Parkway in Fort Belvoir.

Emergency officials also were struggling to rescue numerous drivers on Cinder Bed Road near Newington in Fairfax County, according to police radio dispatches.

Shortly before 8:30 p.m., Fairfax County police put out an urgent call needing additional boats to try to reach “numerous cars with people in them” who had been swept off the road. Children may be in at least one of the vehicles.

“We can see them, we can’t get to them,” one officer stated to dispatch. “I need a second boat. If we lose the cars over the guard rail, we are going to lose them into the VDOT lot and that is a mess. We are running out of options and these cars keep floating into our intersection.”

Fairfax police on dry ground have been using binoculars to determine whether people are still in vehicles that have stalled out in deep water on some highways.

Prince William County officials said they have evacuated two mobile home parks as heavy rain have overwhelmed waterways and tributaries. Holly Acres located off Route 1 and Marumsco Mobile Home Park, near Marumsco Plaza have been evacuated, displacing about 120 to 160 residents. A shelter has been set up at Woodbridge High School, located at 3001 Old Bridge Road. The Red Cross and the Department of Social Services are operating the shelter.

Also in Prince William, county officials said 12 apartment units are being evacuated because a retaining way is in danger of failing. The wall is located off Breezy Ridge Way, just east of I-95 off of the Prince William Parkway.

Road closures

According to the D.C. Department of Homeland Security, Maryland officials are closing the westbound lanes of the Woodrow Wilson Bridge to keep vehicles from traveling into Virginia, where parts of the Capital Beltway are closed due to flooding.

“Drivers should avoid the entire stretch of the Capital Beltway from the Woodrow Wilson Bridge to the Springfield Mixing Bowl,” the District said in an emergency alert. “The road is flooded, and there are multiple road closures.”

Road conditions deteriorated quickly Thursday evening. Virginia Railway Express sent Manassas line trains back to Alexandria due to flooded tracks. Buses were called to pick up passengers.

VRE will not operate trains on either line Friday due to flooded tracks. CSX and Norfolk Southern will need to inspect the tracks and fix a washed out area near Franconia. VRE officials said there shouldn’t be any long-term impacts, but they want to make sure track bed is solid and stable before putting the commuter rail service back in service.

Just after 8 p.m., eastbound lanes of I-495 were closed at the “mixing bowl,” I-66 westbound was closed at Route 50 because of water. Earlier, I-495 was shut down in both directions over Cameron Run near Telegraph Road.

These roadways in Alexandria were closed due to flooding, according to Alexandria officials: Edsall Road at Yoakum Parkway; South Pickett Street at Van Dorn Street. Also, motorists were asked to avoid Eisenhower Avenue from Van Dorn Street to Pershing Avenue.

Fairfax officials also urged residents who live on these roads in the Huntington area of the county to evacuate their homes immediately: Fenwick Drive, Arlington Terrace, Mount Vernon Drive and Liberty Drive. Public questions should be directed to 571-350-1265.

Several roads in Prince George’s County closed during the evening. Though some reopened, at 10:30 p.m. several in Clinton, Upper Marlboro, Bowie and Brandywine remained closed.

Original post, early Thursday afternoon:

Heavy rains across the region bedeviled some commuters as they traveled home Thursday evening as roads, parking lots and other facilities flooded or were otherwise affected by the weather.

The Reston North Commuter Parking Lot for The Fairfax Connector, on Sunset Hills Road. (Courtesy of The Fairfax Connector )

Norfolk Southern had not put any restrictions in place as of 3:45 p.m. Thursday, but could as rain continues in Manassas, VRE officials said. Metro also did not report any rain-related problems on its subway lines Thursday evening; some bus service was affected. MARC did not report any major delays as of about 6 p.m.

Rain flooded the lower end of a park-and-ride used by the Fairfax Connector in Reston, partially submerging dozens of vehicles and prompting the agency to station a bus there as temporary shelter for stranded commuters, a spokeswoman for the transit service said Thursday.

At least a third of the vehicles in the lot west of Isaac Newton Drive in the lower, western end of the Reston North Park and Ride were flooded, Fairfax Connector spokeswoman Ellen Kamilakis said.

Thelot, which is owned and maintained by the Virginia Department of Transportation, can hold up to 368 vehicles and serves the No. 505, 595, 597 and 952 bus lines, Kamilakis said. The 505 runs to the West Falls Church Metro station, the 595 goes to the Pentagon Metro, the 597 serves the Pentagon and Crystal City stations, and the 952 is an express to the West Falls Church Metro, she said.

Kamilakis said the agency has stationed a bus there as shelter and will also shuttle commuters to the Reston Transit Center. The Reston Transit Center will remain open past its regular closing time of 7:00pm, Supervisor Catherine M. Hudgins said in an advisory.

The Fairfax Connector — a bus service provided by Fairfax County and Virginia and operated under contract by MV Transportation — posted a picture of the flooded parking lot on its Facebook page as a heads-up for commuters heading home.

“It was sad to put that picture up,” Kamilakis said. “I think some people are going to be taken off guard.”

Minor flooding was reported around the rest of the county in mostly flood-prone areas such as Huntington and Bellevue areas, according to Dan Schmidt, a spokesman for the Fairfax County Fire and Rescue Department.

Fairfax County officials partially activated the Emergency Operations Center at 4:30 p.m. As of 5:40 p.m., its blog listed more than a dozen road closures, including Route 50 in both directions near the Fair Oaks Mall and the Fairfax County Parkway (Route 7100) at Ox Road.

Other closures include: Walney Road between Willard and Westfields; Fairfax Station Road at Popes Head Mill Estate; Popes Head Road at the Fairfax County Parkway; Route 1 at Dogue Creek; Old Courthouse at Besley; Oberon Way at Capulet Court; 1300 block of Kirby Road; Swinks Mill Road at Georgetown Pike; Prosperity at both ends of Morningside Drive; Baron Cameron/Hunter Mill; Lawyers Road/Hunter Mill; Route 7 at Colvin Run Road and parts of Beach Mill Road

Wright said drivers should be extra careful as roadways can be closed at anytime for safety precautions. She recommended that drivers avoid unnecessary trips.

Roads have been dangerous for days as rains have soaked the region. In a Thursday afternoon press release, the Prince George’s County Fire/Emergency Medical Services Department said its Technical Rescue Team responded to more than 60 calls from stranded motorists on Wednesday and Thursday.

Post staff writer Erica Morrison contributed to this article.

This item has been updated.