A Greyhound bus from Washington flipped onto its side yesterday morning after running off a rain-slicked highway ramp near Baltimore, sending all 33 passengers and the driver to area hospitals, five with severe injuries.

The accident played havoc with the morning rush hour. A portion of northbound Interstate 95 was closed for hours as paramedics and rescue workers treated injured passengers, including two people who were trapped in the bus and had to be pulled out.

The bus, which originated in Atlanta and was headed for Philadelphia, crashed just after 6 a.m. yesterday. During a heavy downpour, the bus driver lost control while changing lanes on the interchange ramp from I-95 to I-895 northbound, authorities said.

The bus flipped onto its right side and landed in the grassy and muddy tree-lined shoulder. The driver, who officials would not identify, told police that a tractor-trailer passed in front of her on the ramp and kicked up water, leading her to lose control.

All 34 people on board were taken to five area hospitals to be checked for injuries, said Baltimore Fire Department spokesman Kevin Cartwright. Authorities did not release the names of the passengers yesterday, and it was not known how many were from the Washington area.

Of 14 injured passengers, five of the most severely hurt were taken to Maryland Shock Trauma Center. At midday yesterday, one was in critical but stable condition and four were in serious but stable condition, hospital spokeswoman Cindy Rivers said.

Police closed I-95 northbound for three hours and detoured morning commuters at the Moravia Road exit. They reopened the highway at 9:22 a.m. The Maryland Transportation Authority is investigating the crash.

Cartwright, who was one of the first authorities to arrive at the scene, said the bus was lying on its side in the grass next to the road.

"The front of the windows were out of the bus, and there was obvious damage to the bus," Cartwright said. There was "a lot of dirt and debris on the tires and under the body of the bus."

Bus No. 532 departed from Atlanta at 12:30 p.m. Sunday and made several stops before arriving in Washington early Monday morning, Greyhound spokeswoman Anna Folmnsbee said. The bus left the District at 5 a.m., about 30 minutes behind schedule, and stopped in Baltimore at the I-95 Travel Plaza. It was to stop in Wilmington, Del., before its scheduled 7:35 a.m. arrival in Philadelphia.

Workers prepare to right a Greyhound bus that overturned on an Interstate 95 ramp near Baltimore early yesterday.