SAN FRANCISCO -- An early Friday morning explosion rocked a three-unit apartment house in located behind a dry cleaners in San Francisco's Amazon Crocker neighborhood, sending two people to the hospital with burns, spraying glass across busy Mission Street and possibly leading to a bicycle-car accident at a nearby corner.

Sgt. Neville Gittens said the blast occurred about 6:45 a.m. at 5153 Mission St. When units arrived, they found the dry cleaners that fronts Mission Street heavily damaged, but quickly turned their attention to an apartment building located in the rear where the explosion had taken place.

The force of the blast had bulged out a wall of the building and authorities quickly evacuated the residents. Two suffered severe burns were at the hospital being treated for burns. The man was suffering from life-threatening injuries while the woman injured in the blast was being treated at St. Luke's Hospital for less severe burns. The other residents were not injured.

Sgt. Michelle Jean could not speculate on a cause, but said police had been to the building before on a drug-related call.

Meanwhile, while authorities were assisting in the explosion a bicyclist was struck by a car on a nearby corner. The bicyclist was treated at the scene for minor injuries.

The explosion and accident closed the busy outer Mission Street corridor for more than an hour.