Mayor Bill de Blasio said he steered clear of Thursday morning’s steam-pipe blast and asbestos scare in Manhattan’s Flatiron District because the terrifying incident wasn’t “serious” enough for him to rush to the scene.

Speaking at an unrelated news conference in the Bronx, de Blasio said that “considering the incident was over and there were no major injuries, that’s a situation where I don’t always go, obviously.”

“I go when something is ongoing or there has been a more serious impact,” he said.

“The situation is under control, the evacuations happened. There are some environmental concerns being looked at. … But in terms of immediate impact, no serious injuries, thank God.”

Despite that explanation, de Blasio headed to the scene following the news conference, with spokesman Eric Phillips tweeting a photo of Hizzoner getting an official briefing and watching overhead drone footage inside a mobile command center.

The FDNY said five people — three civilians, an NYPD cop and a Con Ed worker — suffered “very minor injuries” that didn’t require hospital treatment when the 20-inch steam pipe exploded around 6:45 a.m. near Fifth Avenue and 21st Street.

The incident also sparked fears of asbestos contamination that led authorities to evacuate 28 nearby buildings, and about 100 firefighters who responded were being decontaminated as a precaution.

Officials expect to have the results of asbestos testing later in the day.