Saskatoon police chief Clive Weighill says the deaths of two teenagers has him fed up with the increasing rate of vehicle thefts in the city and the owners who seem to be making the crimes so easy.

Police say a stolen pickup truck sped through a busy intersection Monday night and crashed into two other vehicles. One of them, a car, was pushed on its side and into the wall of a medical clinic.

Two 17-year-olds in the car, a boy and a girl, were killed. A 16-year-old girl who was also in the car was taken to hospital with life-threatening injuries.

The 21-year-old driver and 17-year-old passenger of the truck were scheduled to appear in court Wednesday to face charges in conection with the crash. Charges of impaired driving causing death and criminal negligence causing death are pending.

Weighill said Tuesday that the truck had been easily taken. Its keys were left inside.

"I am frustrated and I mean it," he told a news conference.

"Something like this should never happen in the city of Saskatoon."

Weighill said that in about 70 per cent of stolen-vehicle cases in the city, keys were left inside or were poorly hidden nearby. And despite public campaigns asking people to guard their keys more safely, more vehicles have been reported stolen in recent years.

"Already this year, we're up 28 per cent."

The vehicles that most often go missing in Saskatoon are new pickup trucks -- again with keys left inside, said Weighill.

Matching the chief's vexation with auto thefts was his disdain for repeat car thieves and courts that put many of them back out on the street.

The suspects in Monday's deadly crash -- a 21-year-old woman pulled out from behind the wheel of the truck and a 17-year girl sitting beside her -- have been charged with stealing a vehicle before, he said.

"I'm probably one of the biggest proponents of diversion and helping youth and trying not to send people to correctional facilities," said Weighill. "But in some cases, where we have these repeat offenders, somebody has to say stop."

He gave no details on the pair's past crimes or release dates.

He said they were treated in hospital for minor injuries, then placed in police custody. They are likely to face numerous charges that could include impaired driving causing death and criminal negligence causing death, said Weighill.

They were to appear in court Wednesday.

Weighill dismissed witness accounts that the deadly crash happened during a high-speed police chase.

He said a police video shows an officer had been following the stolen truck for several blocks before he turned on his emergency lights and siren.

"As soon as he did that ... that vehicle immediately sped off at a high rate of speed. Our officer's vehicle slowed right down, did not pursue that vehicle, because he could see that this was not going to end well if there was a pursuit."

Weighill said he hopes the deaths will finally wake up people.

"We can't do this on our own. We're asking people not to leave the keys in their cars. We're asking the prosecutions and the courts to help with some of the repeat offenders.

"It's a frustration when you're caught in the middle as a police service."