Canterbury police are investigating after two police vehicles were found torched in New Brighton overnight.

One was found alight in the secure police station carpark - another one parked next to it was also damaged.

Both vehicles have been damaged beyond repair, and the incident is being treated as suspicious.

Canterbury Metro Commander Superintendent Lane Todd says work is underway to try find out what happened.

He says since first light they've had a fire investigator specialist working alongside detectives to conduct a scene examination, which is still taking place.

"One of the vehicles was well alight, while a second vehicle parked next to it was also on fire," he said.

"[Firefighters] attended and put the fire out. This morning [at] first light we have had a fire investigator specialist with detectives doing a scene examination. That's progressing as we speak.

"We will be pulling CCTV footage and talking to any potential witnesses who may have been in the area at the time.

"It was quite an extensive fire.

"We are very concerned about the incident. The vehicles were in a secure yard. It's one of our 24-hour stations.

"It's a concern for us that something like this could occur. However, it is early days in the investigation and we have to keep an open mind.

Police have asked anyone who has any information has been asked to come forward.

Meanwhile, a man's in custody after an attack on a police officer in Canterbury.

Police were called to a family harm incident in Oxford yesterday afternoon.

Superintendent John Price says the offender allegedly threatened an officer with a knife, and later attacked another through the open window of a Police car.

That officer was hospitalised with lacerations to one arm.

Price says he's in a stable condition and no one else was injured. He says there's always a risk in policing, but assaulting an officer is an assault on the fabric of our community.