At Least 1 Dead After Tornadoes Are Reported in Indiana

At least one person was killed and another was injured in southern Indiana on Sunday when storms battered parts of the South and the Ohio River Valley, causing power outages to hundreds of thousands of customers.

An official in Martin County, Ind., said that one person was found dead and another was injured, but that responders were searching for victims and clearing trees from the roads. A tornado is suspected, but has not yet been confirmed by meteorologists. “This is out here in the middle of the woods,” Monty Wolf, the director of the county’s emergency response team, said by phone. “It’s a mess.”

In Johnson County, at least one tornado was considered likely near the town of New Whiteland, said Chad Swain, a meteorologist with the National Weather Service in Indianapolis. “We have other possible tornadoes, one in Martin County and another one in Monroe County,” Mr. Swain said, adding that multiple homes had been severely damaged.

In northern Indiana, Porter County officials said that severe weather at a local BP refinery had triggered an unplanned flaring of gasses at the facility. Crews were on site managing the situation, officials said, and that there was no immediate danger to the community.

As of early Monday, fewer than 10,000 customers in Indiana were without electricity, according to poweroutage.us, which compiles data from utilities. Farther south in Arkansas, Kentucky and Tennessee, where storms had also ripped through communities, more than 300,000 customers were without power.

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 police department said that officials in the city, which has a population of about 65,000, were still working to evaluate the damage. The dispatcher would not comment on whether anyone had been injured or killed in the storm.

“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.”

Around seven miles southwest in the town of Bargersville, at least 75 homes were damaged after a tornado struck an area three to four miles in length, but no one was injured, officials said at a news conference. Power lines were down, and officials were working to complete a secondary search of the impacted areas, they said.

The Red Cross said it was coordinating with local officials to determine the needs of affected communities. “These needs may include sheltering, access to food and water, health and mental health support and more,” Stephanie Fox, a spokeswoman for the organization, wrote by email, noting that the situation was “actively evolving.”

Mr. Swain, the meteorologist, said that the thunderstorms were spurred by hot and humid air ahead of a cold front. Scientists are not yet able to determine whether or not there is a link between climate change and the frequency or strength of tornadoes. Tornadoes are relatively small, short-lived weather events, and because of that, there is limited historical data on their prevalence in the past; scientists need at least 40 years of weather data before they are able to draw a causal link.

Researchers do say that in recent years tornadoes seem to be occurring in greater “clusters,” and that the area of the country known as Tornado Alley, a region where most tornadoes occur, seems to be shifting eastward. The timing of tornado seasons is also becoming more unpredictable, researchers have found, with more early and late starts compared with decades ago. The reason for this is unclear.

Derrick Bryson Taylor contributed reporting.