A Con Edison substation in Brooklyn spewed dielectric fluid into the East River on Sunday, causing an oil slick that witnesses said could be seen in Queens, and now officials are working to clean up the mess, a Coast Guard spokesperson said today. Coast Guard Chief Warrant Officer Allyson Conroy said a "catastrophic failure" of a transformer at a Con Edison surrogate substation in Brooklyn caused the oil to be released into the river. (Dielectric fluid is a mineral oil used to prevent electric discharges and insulate power cables, among other things.)

The National Response Center received the report of the spill at 1:30 p.m on May 7th. A "safety zone" is currently in effect on the East River, south of a nautical line drawn from Dupont Street in Greenpoint, Brooklyn to East 25th Street in Manhattan, and north of Buttermilk Channel.

"We don't know how long the safety zone will be in effect," Conroy said. While in effect, recreational and human-powered vessels (kayakers, paddle-boarders, etc.) are prohibited from the area. And NYC Ferry has announced that customers should expect delays in East River service for the remainder of today due to the incident; you can follow them on Twitter for updates.

Con Ed spokesman Allan Drury confirmed the spill took place at their substation on John Street in DUMBO Brooklyn.

“Con Edison is working to contain and clean up transformer insulating oil that was released from one of our substations in Brooklyn near the East River," Drury said. "A transformer containing approximately 37,000 gallons of dielectric fluid, mineral oil used for cooling electrical equipment, failed on Sunday May 7th at 12:23 p.m, causing the oil to be released from its main tank. Some oil entered the East River and Con Edison responded immediately, placing boom, absorbents and skimmers in the river. Our own employees and environmental contractors are working on the cleanup, and we are working cooperatively with the U.S. Coast Guard and the New York State Department of Environmental Conservation."

Con Edison is still trying to verify how much of the substance was released into the river, and what caused the failure. Witnesses said they saw an oil slick on the East River from Hunter's Point South Park in Long Island City around 4 p.m. on Sunday afternoon.

We'll update as more information becomes available.

UPDATE 3:52 p.m.:
Con Edison released an official statement this afternoon:

Con Edison is working to contain and clean up transformer insulating oil that was released from one of our substations in Brooklyn near the East River. A transformer containing approximately 37,000 gallons of insulating oil used with electrical equipment, failed on Sunday May 7 at 12:23 p.m., causing much of the oil to be released within the station property in addition to the East River. The equipment failure also caused a system voltage dip that impacted the MTA’s signaling systems on Sunday, resulting in a disruption to some train service. Con Edison responded immediately, placing boom, absorbents and skimmers in the river. Our own employees and environmental contractors are working on the cleanup, and we are working cooperatively with the U.S. Coast Guard, the New York State Department of Environmental Conservation and other agencies. We continue to assess the volume of oil that migrated to the East River, and how much oil remains in the ground on our property. The Coast Guard has issued reduced speed restrictions for commercial vessels operating in the area, and banning recreational vessels, to assist the cleanup process. We are taking all actions to contain and clean up the oil as safely and as quickly as possible.

Additional reporting by Jeanmarie Evelly.