Dense fog contributed to a fiery chain-reaction crash today involving 71 cars, vans and trucks on the Sam Houston Tollway. Police said 21 people were injured, five seriously, but there was no fatalities.

The pileup started just before 7 a.m. on the four-lane highway and involved traffic in the eastbound and westbound lanes.

"It was kind of a wall of fog," said Mike Young, 45, who was driving to work. He said he climbed out of his sport-utility vehicle to safety while hearing crash after crash.

"When everyone was getting out, you could smell the gas and knew there would be a problem," Young said.

The wreckage prevented firefighters from reaching the blazing vehicles, said Kenneth Fonenot, whose SUV was destroyed in the flames.

Roger Ealey said he dived out of his car when he saw it was about to ram a pickup that had no lights. He suffered minor injuries, and his car became lodged under the pickup.

You couldn't see anything because the fog was as thick as "pea soup," said Ealey, 27, of Missouri City.

Capt. Ray Valenta of the Harris County Constable's Office said 36 cars were wrecked in the westbound lanes and 35 in the eastbound lanes on the highway in southwest Harris County.

Wrecked cars and emergency vehicles are scattered across the Sam Houston Tollway after "a wall of fog" triggered a massive pileup and fiery crash.