A huge explosion leveled a townhouse building on Manhattan's Upper East Side Monday, injuring several people, and fire officials were investigating whether the blast was the result of a suicide-by-gas attempt by a doctor who owned the building and was going through a bitter divorce.

A police official with direct knowledge of the case told The Associated Press that Dr. Nicholas Bartha recently sent out an e-mail to his wife in which he contemplated suicide and said, "You will be transformed from gold digger to ash and rubble digger." The official spoke on condition of anonymity because the investigation is ongoing.

At least 15 people were injured in the blast, which leveled the four-story New York City building into a smoky pile of rubble.

2005 Divorce Ruling (Bartha v. Bartha) (FindLaw PDF)

"There was so much blood," said Karen Morris, a nurse who aided victims and treated survivors for welts, splinters and cuts.

Among the wounded were 10 firefighters and five civilians, including Bartha, who was listed in critical condition at a local hospital. The doctor, who specializes in emergency medicine, was pulled from the rubble after using a phone to communicate with authorities, sources said.

The blast scattered bricks, glass and splintered wood across the block and shattered windows in a neighboring building. Several people were carried off on stretchers as firefighters doused the structure's remains.

Across the street in the Regency Hotel, visitor Allan Schare and his family were jolted from sleep. "I heard and felt the explosion — my kids levitated out of bed," he said. "We first thought: Earthquake. We're from Los Angeles."

Counterterrorism officials told FOX News there is no evidence to indicate the blast is related to terrorism but investigators were probing Bartha's electronic communication, New York City Fire Commissioner Nicholas Scoppetta said.

As part of the adjudication of the divorce, Bartha, 66, is being made to sell the building, sources said. Officials said Bartha was apparently losing the home because of the divorce, and court records show that he faced a $4 million lien as a result of the case. The building is located in an upscale neighborhood where the 2000 Census said the median price of a home was $1 million. The edifice housed doctors' offices and six apartments.

Power company Con Edison said its crews had been responding to complaints from a gas customer at an adjacent building when the blast occurred. Gas also was shut off to three nearby buildings.

Heavy black smoke rose high above the building, wedged between taller structures on 62nd Street between Park and Madison Avenues just a few blocks from Central Park. Damage, including shattered windows, could be seen at one of the adjoining buildings.

"The building adjacent to the structure that collapsed had some damage … five to 10 of the front windows had been blown out," Red Cross spokesman Michael Virgintino said.

Yaakov Kermaier, 36, a resident in a building next door, said he was outside when he heard "a deafening boom. I saw the whole building explode in front of me."

"Everybody started running, nobody knew what was coming next," he said. His nanny and newborn escaped from their next-door apartment unharmed.

The Red Cross was meeting with people evacuated from nearby buildings, Virgintino said.

"We were told to leave the building," said area resident Vivian Horan.

Thad Milonas, 57, was operating a coffee cart across from the building when he said the ground shook and the building came down. Milonas said he helped two bleeding women from the scene.

The building is an upscale neighborhood where the 2000 Census put the median home price at $1 million. On one corner of the street is the high-end Luca Luca clothing store, and across the street is the French retailer Hermes.

FOXNews.com's Heather Scroope and The Associated Press contributed to this report.