Authorities were searching for a man who threw a "homemade pyrotechnic device" containing gunpowder into a crowded downtown Pasadena restaurant Thursday night, sending diners scrambling for cover, police said.

Nobody was hurt in the explosion after 6 p.m. at the Cheesecake Factory on Colorado Boulevard in Old Pasadena, according to police. As of Friday morning, nothing suggested that it was "anything other than a really bad prank," said Lt. Vasken Gourdikian of the Pasadena Police Department.

The device was a "glorified firecracker" that didn't appear to be made to injure anyone, a police spokesman said Friday.

Police safely evacuated diners from the restaurant and found the expended device, according to a Pasadena Police Department news release.

Untouched plates of food and personal belongings were left behind in the deserted restaurant.

"People were jumping over one another, fighting to get over bar stools. People were tripping, falling...stuff going everywhere. It was very chaotic," said Garrett Gunkle, who went back to the scene to try to collect the belongings he left behind.

A man opened the door of the restaurant, lit the device, threw it inside and fled southbound on Fair Oaks Avenue, police said. The device landed under an unoccupied table.

Gunkle said he saw an explosion, and he and his wife bolted out of the restaurant as quickly as possible.

"According to the Los Angeles County (Sheriff's Department) Bomb Squad, it was a crude, homemade pyrotechnic device," Gourdikian said. "It wasn't meant to be destructive in the sense that it didn't have associated fragments or shrapnel. It was intended to make a loud bang, which is what it did. It's still harmful, but it wasn't intended to injure or maim."

The man who threw the device was described as about 6 feet tall with a thin build and heavy beard. He wore all black clothing and a black beanie.

The motive is not known, police said.

The Cheesecake Factory, police, and the FBI did not receive any threats, Gourdikian said.

A spokeswoman for the Cheesecake Factory, Alethea Rowe, gave the following statement to NBC4 Southern California Friday morning.

"This evening, an incendiary device exploded within our Pasadena restaurant. Thankfully, none of our guests or staff was injured. Law enforcement is actively investigating the incident, and we hope to reopen in Pasadena on Friday, as usual," read the statement.

Anyone with information can reach Pasadena police at 626-744-4241. Tips may also be submitted anonymously to L.A. Regional Crime Stoppers at 800-222-8477.

Jonathan Gonzalez and Jessica Rice contributed to this report.