At least 15 large trucks were involved in a massive pileup that killed at least two people on a snow-bound highway in the US state of Indiana Thursday, officials said.

"Many more" fatalities could be discovered when emergency crews are finally able to search the cars trapped underneath the big rigs, LaPorte County Coroner John Sullivan told NBC news.

"It's just a mess out there right now," Sullivan told the station's Chicago affiliate.

Indiana State police said white out conditions, high wind and extreme cold led to a "numerous" other crashes in the area and urged people to stay off the roads.

"We want to make sure we take care of the people who are in this back-up now and not add to it," the state police said in an advisory.

Footage shot from a news helicopter showed traffic backed up for miles as heavy snow continued to fall on the highway outside Michigan City, which is near the border between Indiana and Michigan.

Crushed cars could be seen littered among the jackknifed trailers, which had smashed together in a messy pile that spilled off the road.

Neither the coroner nor the state police immediately returned requests for comment.