A hole being excavated for a new subway station collapsed, opening a huge crater that swallowed cars and dump trucks, and firefighters aided by dogs searched the site Saturday looking for a missing minibus that was feared under the dirt.

A bus cooperative reported a minibus carrying as many as eight people was missing and may have tumbled into the crater Friday when part of a street adjacent to the site slid in, said Etrusco Juarez of the Security Department in Sao Paulo, South America's largest city.

He said authorities had not confirmed the van fell into the hole, which was about 200 feet across, but were searching, Juarez said.

Local media said the minibus was carrying a driver, a fare collector and four to six passengers.

There were news reports that three construction workers were injured when the walls of the excavation site gave way, but the state-owned subway company and fire department could not confirm that.

Two cars were removed from the rubble overnight and a towering crane that had threatened to topple into the hole was stabilized, the Security Department said.

The cause of the collapse had not been determined.