COBB - Investigators have concluded that a Dec. 20 fatal crash on Interstate 20 was due to a rotten tire blowing out. Cobb police are urging motorists to check tires for cracks and tire tread wear to avoid such accidents from occurring in the future.

The accident happened at 1:21 p.m. on I-20 between Factory Shoals Road and Riverside Parkway in Austell. After the blowout, the 2003 Ford Explorer overturned and the six occupants were ejected. Passenger Adriana Gil, 29, of Forest Park, was pronounced dead at the scene. Another passenger, Rocia Jimenez, 29, of Forest Park, died later at Atlanta Medical Center. The four others were transported to AMC and Grady Hospital with serious injuries.

"Drivers should check the date of manufacture of the tire, check for cracks and breakdown in the sidewall of the tire, and monitor the tire tread," Cobb Police spokesman Officer Joe Hernandez said.

Even if the tire has good tread depth, it could still be bad, said Chris Weaver, service manager at Weaver Brake and Tire on Manget Street in Marietta. Minimally used tires still rot, he said.

Weaver said rotting tires will have fine cracking in the sidewalls similar to cracks in dry skin. Those cracks can also be seen in the tread.

Weaver also suggests that people pay attention to the DOT Tire Identification Number that is stamped on every tire. The last four numbers on the stamp tell the week and year the tire was produced. For example, 1204 would mean the 12th week in 2004.

"Regardless of when the tire was put on, it could have sat in stock for three to four years," he said. "That number tells customers how old the tire is."

He said dealers are prohibited from selling tires that are five or more years old.

He said, typically, the safe lifespan of a tire is seven to 10 years.

Weaver also warned of cold weather reducing tire pressure. He said cold weather will generally reduce tire pressure by four pounds, which could be dangerous, especially if a motorist is already driving on underinflated tires.