Officials claimed on Saturday that at least 16 tourists perished in frigid conditions after being trapped in their vehicles in northern Pakistan, where hundreds had traveled to enjoy the snow.

The government has designated Murree, 64 kilometers (40 miles) northeast of the capital Islamabad, a tragedy stricken region, with over 1,000 cars still trapped.

“For the first time in 15 to 20 years, such a significant number of visitors rushed to Murree, causing a major issue,” Pakistan’s interior minister, Sheikh Rashid Ahmed, said in a video message.

The minister said that around 1,000 cars were stuck in the hill station, a town elevated from the nearby area, confirming that “16 to 19 deaths have occurred in their cars.”

Army platoons and paramilitary forces have been deployed to help the civil administration in rescue operations, he said.

Late on Friday the government announced the closure of all roads leading to the station to stop any further influx of the tourists.

Prime Minister Imran Khan expressed shock over the “tragic deaths” of the tourists. “Have ordered inquiry and putting in place strong regulations to ensure prevention of such tragedies,” Khan said in a tweet.

Information Minister Fawad Chaudhry appealed to people to not visit the hill station.

Snowfall, which began on Tuesday night, continued at regular intervals, attracting thousands of tourists. Due to huge numbers of visitors, many families ended up getting stranded on roads.

Local media reported that over 100,000 vehicles entered the hill station.

Videos shared on social media showed entire families, including children, lying dead in their snow covered vehicles.

“Were the deaths caused by cold or carbon monoxide (CO) poisoning?,” Dr. Faheem Yonus, chief of infectious diseases at the University of Maryland UCH, said in a tweet. “CO is odorless, lethal if an idling car is buried in snow, the blocked exhaust (silencer) can quickly kill the passengers as they breath CO.”

Officials have given no word on the causes of the deaths.