A 78-year-old Washington woman was killed in a fiery explosion yesterday when the taxicab in which she was riding with three other passengers swung out of control and crashed in flames on the Taft Bridge over Rock Creek Park.

The ABC cab, heading south across the bridge and Connecticut Avenue NW in early-morning rush-hour traffic, suddenly mounted the right hand curb and burst into flames when the gasoline tank ruptured and its contents were ignited by sparks from the dragging undercarriage, D.C. police reported.

The cab crashed into the bridge guard railing and became engulfed in flames, killing passenger Lillian R. Levine, of 3003 Van Ness St. NW, a retired Veterans Administration employe, police said.

Driver of the cab, James J. King, 63, of 6500 Luzon Ave. NW, was pulled from the wreckage with burns of the face, neck, arms and hands. He was listed in good condition yesterday at George Washington University Hospital.

Two of the other three passengers suffered minor injuries. Amos Kroencke, of Kansas City, Mo., was treated and released for hand burns at George Washington Hospital. Richard E. Jurgella, of Stevens point, Wis., had his hair singed, police said. Larry Wadler, of Oakland, Calif., was uninjured, they reported.

All three surviving passengers were in the rear seat of the cab, police said, and escaped from the left rear door. Levine, riding in the front passenger seat, was trapped when the right front door jammed against the guard rail, police said. She attempted to escape through the left front door but was overcome by flames and smoke they said.

The explosion, which police at first thought had been caused by a bomb, tied up traffic for two and a half hours. Inbound commuters were rerouted onto Calvert Street and the Ellington Bridge over Rock Creek Park.

The matter has been referred to the U.S. Attorney's office and the corporation counsel. Police said King was driving with a suspended driver's license at the time of the accident.