SAN DIEGO — The Fourth of July fireworks show went off with a bang over San Diego Bay. Too big a bang.

The Big Bay Boom show that was supposed to wow crowds for 20 minutes lasted only about 20 seconds after a computer mishap caused multiple bulb-shaped explosions on the bay, lighting the night sky and filling the air with deafening booms.

The show’s producer blamed a ‘‘technical glitch’’ Thursday, saying an error in its computer system caused tens of thousands of fireworks on four barges to go off simultaneously with a single command.

‘‘Thank goodness no one was injured. Precautions all worked 100 percent,’’ said August Santore, part-owner of Garden State Fireworks.

Garden State Fireworks, based in Millington, N.J., apologized and vowed to determine precisely what went wrong. The 122-year-old company produced hundreds of other shows on Wednesday night.

Spectators complained it was not immediately clear the show was over.

Sponsors contributed about $380,000 to host the show, said Sandy Purdon, owner of a bay marina and the chief organizer. The Port of San Diego contributed $145,000 as title sponsor, with hotels and restaurants giving much of the rest.

ASSOCIATED PRESS