UPDATE: Emergency meeting called on underground blasts downtown

Underground explosions caused by electrical arcing shot manhole covers into the air at a busy downtown Indianapolis intersection on Thursday, disrupting commuters, closing businesses and raising concerns about safety as the city prepares to host the Final Four next month.

Indianapolis Power & Light officials said Thursday that the arcing — electrical current jumping a gap in a circuit — occurred in 120-volt underground cables and caused the system to short-circuit.

"We do have significant damage to the electrical infrastructure," vice president of customer operations Joe Bentley said during a news conference.

No one was injured, but several buildings were evacuated as a precaution, including an apartment complex where high levels of carbon monoxide were detected. Hundreds of customers lost power, and IPL said Thursday afternoon that about 150 customers in a four-block area could be without electricity into the weekend while equipment is repaired.

The Indiana Utility Regulatory Commission scheduled an emergency conference with IPL for Friday to discuss the issue, which is the latest in a series of blasts that started in 2005.

"This is a real serious situation, and we've got some questions and we need to talk about it now," spokeswoman Natalie Derrickson said.

Bentley stressed that the system is safe and said the utility was working to prevent additional issues.

He said Thursday's blast was not related to an issue Monday night, when smoke and fire began spewing from a sidewalk grate along Massachusetts Avenue in the city's downtown business district. IPL said the fire was ignited when equipment in an underground electrical vault malfunctioned.

More than a dozen similar incidents have occurred in Indianapolis over the last decade. In 2005, at least three blasts occurred in a nine-day period, including one near the Indiana Statehouse that injured three people and damaged a bookstore. Those blasts were blamed on a series of short-circuits in underground utility lines caused by heavy rains and freezing and thawing.

In 2011, IPL blamed electrical shorts for a half-dozen explosions that sent manhole covers, which can weigh as much as 160 pounds, flying, damaged vehicles and raised concerns about the safety of those planning to attend the 2012 Super Bowl. Those blasts prompted state utility regulators to commission a study examining the cause of the blasts and the utility's maintenance practices.

IPL that year installed about 100 new manhole covers near Lucas Oil Stadium that were designed to reduce damage from underground explosions and fires. Bentley said it has now replaced 357 of about 1,000 covers with the swivel-lock lids, which pop up 4 to 6 inches to relieve pressure in an explosion. The utility is replacing 50 to 100 of the covers each year, he said.

Indianapolis Department of Public Safety spokesman Al Larsen said his agency would work with the utility to conduct safety inspections in key downtown areas once repairs are made from the latest incidents.

He acknowledged that the upcoming Final Four, scheduled for April 4 and April 6, creates a sense of urgency

"We know we obviously have a very big event coming up in less than three weeks where we're going to have the world descending on Indianapolis," he said. "We want to make sure we've got it all buttoned up."