NEW DELHI (AP) — Opaque, chilly smog blanketed northern India on Monday as low temperatures collided with hazardous levels of air pollution.

Across many cities in the region, including New Delhi, the capital, visibility was reduced to 200 meters (218 yards), according to the India Meteorological Department.

Six people were killed when their car skidded off the road and tipped into a canal in a suburb of New Delhi, apparently because of the poor visibility, the Press Trust of India news agency reported.

With temperatures dropping in New Delhi to 1 degree Celsius (34 Fahrenheit), street vendors, auto rickshaw drivers and people who sleep on the streets of the capital wrapped themselves in hooded sweaters and blankets, and warmed their hands over small bonfires. The city was set to register its coldest December day since 1901.

The fires worsened New Delhi’s notorious winter air pollution, with the air quality index — a measure of ozone, carbon dioxide and particulate matter — topping 500 at a monitor at the U.S. Embassy, 10 times what the World Health Organization considers safe.

Pollution has made the air colder, mixing with moisture under low wind conditions to create low-altitude clouds stretching from eastern Pakistan to India’s eastern state of Bihar, said Rajendra Kumar Jenamani, a scientist with the India Meteorological Department.

The cold and fog were expected to continue through New Year’s Day, government weather data showed.