With all the hot spots extinguished and only a few traces of smoke remaining, a team of investigators Wednesday combed the site of the burned-out University Village apartment project to try to determine what caused the blaze.

Investigators sifted through the burnt rubble hoping to learn where the fire started and how it developed. Lead investigator Don MacAlpine of the Fresno Fire Department said it was too early to rule out anything.

"Arson could be involved, but then there are so many other things that could be responsible," he said.

MacAlpine is part of a team that includes other fire department investigators and a crew from the federal Bureau of Alcohol, Tobacco and Firearms.

It is not uncommon for local authorities to summon help from ATF experts, who are equipped with special equipment and a vast knowledge of different types of fires.

Construction on University Village, a three-story student apartment complex just west of California State University, Fresno, started last July, with the building scheduled to open in August. The 105-unit, 406-bed project was valued at $16 million.

About 4:30 a.m. Tuesday, a fast-burning fire broke out in the middle of the complex.

Dozens of residents from apartments next to the complex were forced to evacuate their homes. Heat from the flames and hot embers damaged several occupied apartments, and about three dozen parked vehicles were damaged, some beyond repair.

While air quality has been ranked as unhealthy for selective groups, officials at the San Joaquin Valley Air Pollution Control District indicated that the fire was not a significant factor. The main problem is ozone, not particulates that are generated by a fire.

Two firefighters suffered minor injuries in the blaze, including one who was treated for second-degree burns on his hands. He was injured while working to keep the fire from spreading to a nearby apartment complex.

A young woman reportedly broke a leg when she slipped on the wet pavement while evacuating one of the apartments.

In addition to examining the burned ruins for evidence, MacAlpine said, investigators will be knocking on doors to talk to neighbors and will interview the firefighters who were first to arrive.

Firefighters have received a "significant amount of help" from witnesses, MacAlpine said.

The ATF team brought a dog trained to detect products commonly used to start fires.

Pending further investigation, the burned site is being treated as a crime scene to protect any evidence. Yellow tape has been strung up around the complex, and Fresno police officers have been posted nearby.

Fire Capt. Clint Nichols said investigators are checking into reports that some people had been entering the construction site at night to hold parties in the nearly finished buildings.

The construction site had a fence around it, and gates were locked when workers were away, but there were no security guards assigned to the site.

Jason Wills, vice president of the developer and property manager, American Campus Communities of Austin, Texas, said the company was pleased with how the project had been progressing and with the response from the student community.

Wills, however, said it is too early to say when or whether the project would resume.

At the same time, Wills pointed to what happened two years ago when a fire destroyed several units under construction at another American Campus Communities project at Lamar University in Beaumont, Texas.

After that fire, which resulted in the arrest of one of the construction workers on felony criminal charges, not only was construction resumed to complete the first phase of the project, but a second phase also was completed and a third phase is being planned, he said.

In Fresno, Wills said, a telephone bank has been established at the company's leasing office at Cedar and Barstow avenues to help handle all inquiries from students who had applied to move into University Village.

As of Wednesday morning, he said, about 60% of those students and their parents had been contacted and that letters were mailed to all of them.

He said the plan is to return all deposits and other fees collected from the applicants and to help students who were affected by the fire to find other housing near Fresno State.

Meanwhile, not everyone is happy with the University Village project.

Mike Cadwallader, 52, a resident of the Arbor Place apartments just west of the project and one of those who had to evacuate his home Tuesday morning, said he is considering leading a drive to prevent the project from resuming.

Cadwallader said he is not only opposed to a three-story building next door, but he also is concerned about what the additional traffic from 400 people living in the complex will do to the neighborhood.

Cadwallader said he also is not happy that no security guards were hired to protect the construction site at night.