(Reuters) - An SUV driven by a 73-year-old man plowed into a Mardi Gras parade crowd in Alabama, on Tuesday, injuring a dozen members of a high school marching band, but there was no sign the incident was intentional, city and police officials said.

Three of the 12 students were in critical but stable condition, a spokesman for the coastal city of Gulf Shores, Grant Brown, said at a news conference. Officials initially said four students were critically injured.

The driver, who was not identified, did not suffer any injuries and has not been charged.

"This was not involving drugs or alcohol, nor is there any indication that this was an intentional act," Gulf Shores Police Chief Edward Delmore said. "Every indication is that this was just a tragic accident by an elderly man driving his vehicle."

The incident occurred after the Gulf Shores High School band led the annual Mardi Gras parade down a state highway shortly after 10 a.m., followed by a 2008 Ford Expedition that was part of a group participating in the parade, Brown said.

"And then something went terribly wrong and that vehicle that was behind the band accelerated and struck the children," Brown said.

The parade was canceled after the incident.

Police were gathering video footage and eye-witness accounts to help determine what caused the driver to lose control, according to Delmore. The driver was cooperative, offering statements and blood samples voluntarily.

Alabama Governor Robert Bentley said in a statement that he had directed the state law enforcement agency to coordinate and assist local police.

The incident came just days after a drunk driver was accused of hurtling a pickup truck into a crowd of spectators at a weekend Mardi Gras parade in New Orleans, injuring 28 people in a crash that brought chaos to the city's signature celebration.

The Gulf Shores Mardi Gras parade dates back to 1978.

"This is the parade that's been going on for 39 years. These are our children, these are our people," Brown said. "I don't know how this happened. It is horrible."

(Reporting by Letitia Stein and Gina Cherelus; Editing by Colleen Jenkins and Leslie Adler)