SEATTLE -- A broken 24-inch water main shut down the University Bridge Wednesday morning and caused a sinkhole that enveloped two vehicles and left some local residences and businesses without water service.

The break occurred underneath the bridge, spewing water around its foundation and causing concerns about the bridge’s structural integrity.

VIDEO: Sinkhole Closes University Bridge

As of early afternoon, the bridge was still closed to traffic.

The sinkhole was reported at 7:36 a.m., and the bridge was closed at 7:45 a.m. as a precaution. Water to the broken main was turned off by crews by about 10 a.m.

Two unoccupied, parked cars fell into the sinkhole when the earth collapsed. The city said it is hiring a crane to remove the damaged vehicles.

RAW VIDEO: Chopper 7 Over Sinkhole

The cause of the break is not yet known. Mayor Greg Nickels said there is no construction in the area so the pipe apparently just gave way.

Nickels said the bridge will remain closed until it is determined to be safe and said he's concerned the foundation of the bridge is being undermined.

VIDEO: Businesses Closed Near Sinkhole

"We're concerned about the water main, but we're more concerned about this bridge," said Nickels, speaking during live coverage on KIRO 7 Eyewitness News.

A section of Portage Bay Place remains closed underneath the south end of the bridge as is Eastlake Boulevard just south of the bridge, but the Seattle Transportation Department said the bridge will be able to lift open so that boats can pass through the Lake Washington Ship Canal.

Gregg Hirakawa said the mechanism was not affected by the broken water main sinkhole, but the sinkhole undermined the soil on the south side of the bridge so it will have to be assessed before the bridge reopens to vehicle traffic.

According to Seattle Public Utilities, areas of Eastlake and Capitol Hill neighborhoods north of East Shelby Street are without water service due to the break.

Some Metro buses that cross the bridge are being rerouted. Metro officials said routes 49, 66, 70, 71, 72 and 73 are affected by the closure. For more information, call 206-553-3000 or go to Metro's Web Site for more details.

Officials said only one leak in the cast iron water main has been reported in the last 15 years.

A 20-inch water main erupted and flooded several streets and businesses in the city's South Lake Union neighborhood on April 25.