Several tornadoes were reported in Indiana on Sunday, destroying structures and leaving people trapped as high winds and tennis ball-sized hail lashed the city of Greenwood and other places south of Indianapolis, the authorities said.

An official in Martin County said that responders were searching for victims and clearing trees from the roads. “It’s all just happening at once right now,” Monty Wolf, the director of the county’s emergency response team said by phone.

Clips posted to social media appeared to show a tornado ripping through the city of Greenwood, Ind., thrusting debris into the air. A dispatcher with the city’s police department said that officials in the city, which has a population of about 65,000, were still working to evaluate the damage.

“Please stay clear of areas affected by this evening’s weather as many areas around Johnson County have tornado damage,” the Greenwood Fire Department said on Facebook, urging people to drive with caution and plan alternate routes.

Cole Basey, a high school student in Greenwood, said that he was at a friend’s graduation party as the tornado approached. He and his friends found refuge in a basement and emerged to find downed trees and a nearby home flattened. “I’d never seen anything like that,” Mr. Basey said. “So it kind of freaked us out.”

As of Sunday evening, tornado watches remained in effect for several counties in Indiana and Kentucky.