The explosion damaged the school's wall, the signboards of the shops in the nearby area and shattered windowpanes of cars parked.

Delhi Fire Services officials said they received a call about a blast near the boundary wall of CRPF school at 7.50 a.m.

"We immediately rushed two fire engines to the spot. There was no fire and no one was injured due to the blast, so our vehicle returned," the officials said.

Fortunately, no injuries were reported in the incident.

A police team after getting information about the incident arrived at the scene and cordoned off the area.

A bomb detection squad and sniffer dogs have been pressed into service.

Forensic teams and officers of the Delhi Police Special Cell were trying to identify the nature of the blast.

The National Security Guard has been informed and a team may visit the spot.

Special CP (Special Cell) R. P. Upadhyay has reached the spot.

CCTV footage of the area was being reviewed to find out the clues.

According to police, an underground sewage line was being examined as part of the probe.

Police sources said a crude bomb could be behind the blast.

An eyewitness said the noise was so loud that he was feeling dizzy.

Another eyewitness said he saw a thick cloud of smoke billowing and heard a loud noise.

The investigation was underway, the police said.

The incident comes close on the heels of various airlines receiving bomb threats.

Over 70 flights were either grounded or diverted due to the bomb threats.