An explosion rocked a hotel under construction Monday, ripping off part of the building's facade, sending debris flying and injuring 14 workers, five critically, authorities said.

Some of the workers were burned and others were injured by debris, fire department spokesman Maurice Luque said. The building did not burn after the explosion, which Luque said appeared to be accidental.

Matt McBride, general manager of the Tin Fish bar about 150 yards (140 meters) away, said he was setting up the outdoor patio bar when the blast occurred. He said he and other workers froze as they saw smoke come out of the building but no flames.

• Click Here for Photos of Blast-Damaged Hotel

"It looked like a bomb," McBride said. "It shook the whole building like a bomb. The reverb was what scared us. Everybody was saying bomb, bomb, bomb, terrorist, terrorist, terrorist."

San Diego Deputy Fire-Rescue Chief Perry Peake said the explosion occurred in an area of the building containing gas, electric and other utilities and that it appeared to have been caused by a mechanical failure or gas.

"We want to rule out all possibilities before making an official report, but we're pretty confident that's how it's going to come out," he said.

The Hilton hotel near the San Diego Convention Center showed serious damage and debris littered a driveway beneath one corner of the structure. Facade material dangled from the structure, drapes dangled out windows and a large equipment room with tanks and pipes was left exposed.

The blast damaged floors four through seven, Mayor Jerry Sanders said.

Firefighters searched the building to determine if there were any other victims. More than 400 construction workers were at the site at the time, Sanders said.

Three of the five workers in critical condition were in a hospital burn unit, Luque said. Nine others had injuries ranging from serious to minor, authorities said.

UCSD Medical Center was treating 10 injured, said Dr. Irving Jacoby, attending emergency room physician.

"They talked about a bright light and an intense heat," said Dr. Bruce Potenza of the hospital's burn unit.

The Padres major league baseball team, which plays at Petco Park across from the convention center, planned to host the St. Louis Cardinals on Monday night as scheduled, said Sandy Alderson, the team's chief executive officer.

Bruce Ragland, who runs an entry gate at the stadium, said he was looking right at the building when the explosion blew through two sides and there was a strong shock wave.

"It was just like watching a Bruce Willis movie, like you know, `Die Hard,"' Ragland said.

The 30-story Hilton San Diego Bayfront hotel was scheduled to open in December, according to Hilton's Web site. It will have 1,190 rooms and more than 165,000 square feet (15,330 square meters) of meeting space.

Karima Zaki, Hilton Hotels Corp.'s vice president for new development for the San Diego hotel, said she did not know if the hotel would open on schedule. She said Hilton had not taken possession of the hotel from the builder, Hensel Phelps Construction Co.

A woman who answered the phone at Greeley, Colorado-based Hensel Phelps' Southern California regional headquarters referred questions to executives at the site, who were not immediately available. Hensel Phelps officials did not immediately respond to questions sent by e-mail.