AUSTIN (KXAN) — The National Highway Traffic Safety Administration is expanding its investigation into carbon monoxide problems with Ford Explorers.

The agency — in a report, Thursday night — says they’ve learned the police interceptor version of the Ford Explorer is experiencing exhaust manifold cracks, which could explain the exhaust odor.

They expanded the investigation after getting nearly 800 complaints about the 2011-2017 Ford Explorer models.

More than 20 Austin police officers have been treated and released after carbon monoxide may have leaked into their patrol vehicles.

Austin police are considering pulling all of its 397 Ford SUVs off the streets. A city spokesperson told KXAN discontinuing the use of its Ford Explorers is just one of the options they’re considering.

The NHTSA, along with representatives from Ford, have been in Austin investigating the vehicles. Ford claimed the problem is not with their cars but the modifications made to the vehicles after they are purchased. However, in a statement Thursday evening, the car maker said it was continuing to investigate.

“Safety is our top priority. A dedicated Ford team is working with police customers, police equipment installers, Police Advisory Board members and NHTSA to investigate reported issues and solve them,”

Ford has established a hotline for customers who have concerns about Explorers or the police edition of Explorers:  1-888-260-5575.