By Dave Kaup

ATCHISON, Kansas (Reuters) - More than 100 people were treated for respiratory problems after a chemical spill at an MGP Ingredients Inc facility on Friday generated a chemical cloud over the northeastern Kansas city of Atchison before authorities declared the threat over.

Authorities evacuated children from local schools, urged residents to remain in their homes and advised people not to enter the city of about 11,000 people located about 50 miles (80 km) northwest of Kansas City, Kansas. They later said the cloud had dissipated and the danger had passed.

The two chemicals involved in the spill were identified by a city official as sulfuric acid and sodium hypochlorite, which mixed to create a chlorine cloud. MGP Ingredients makes bourbon and rye whiskeys, gins and vodkas, according to its website.

"The cloud was massive," Atchison Fire Department Chief Ted Graf said. "I'm not even sure how to describe it."

Seventy-two people were treated locally for respiratory discomfort and an additional 30 received treatment at regional medical facilities, although the injuries were minor, said Trey Cocking, Atchison city manager. Cocking described the effects of the chemical cloud as being like mustard gas, a chemical weapon.

Cocking said on Friday evening that the U.S. Environmental Protection Agency had declared the area clear after completing air-quality tests.

"I honestly couldn't tell if it was fog or the chemical cloud," said Megan Laflin, 24, of Atchison, who shot a video of the cloud from her parents' house. "I couldn't see two feet in front of me."

The incident occurred at around 8 a.m. when the two chemicals were mistakenly mixed at the MGP Ingredients facility after one was brought in by a semi-tractor tanker, Cocking said.

Founded in 1941, MGP Ingredients employs 320 people, according to the company's website.

"MGP Ingredients has reported the event to the EPA and Kansas and local authorities, and is cooperating fully to investigate and ensure that all appropriate response actions are taken. MGP has also engaged outside experts to assist the investigation and response," the company said in a statement.

"There was no significant damage to its Atchison plant as a result of this incident," it added.

Cocking said cleanup work was under way at MGP on Friday evening.

(Additional reporting by Timothy Mclaughlin in Chicago and Ben Klayman in Detroit and Melissa Fares in New York; Editing by Will Dunham and Cynthia Osterman)