Six schools in Delhi received bomb threats over email early on Friday, triggering a multi-agency search of their premises, officials said.
The latest threats come on the back of at least 44 schools receiving similar emails on December 9. Police had declared those threats as hoaxes.
Reacting to the development, former Delhi chief minister Arvind Kejriwal pointed out that it was the second such instance within a week and asked how these bomb threats would affect the children.
A Delhi Fire Services official said, "We received calls (regarding the threat emails) from Bhatnagar International School in Paschim Vihar (4:21 am), Cambridge School in Shri Niwas Puri (6:23 am) and DPS Amar Colony in East of Kailash (6:35 am)."
"(Calls were also received) from the South Delhi Public School in Defence Colony (7:57 am), Delhi Police Public School in Safdarjung (8:02 am) and Venkateshwar Global School in Rohini (8:30 am)," he added.
The fire department, police and bomb detection teams, along with dog squads, have reached the schools and are conducting checks, the official said.
The schools' authorities sent messages to guardians to not send their wards for classes or take them back if they already reached.
A police source said the emails were received at 12:54 am, with the sender mentioning "parent-teachers' meeting" and "sports day" activities in the schools.
The sender also mentioned that the "schools will face bomb blasts" on Friday and Saturday, the source said.
A police official said checks were underway.
Cambridge School principal Madhavi Goswami said she was checking the school mail, as routine, when she saw the threat.
"I informed the police and they worked proactively. We were assured by the Delhi Police about the investigation. We informed the parents that classes would be online today," she said.
Karmveer, a guard at South Delhi Public School, said he received a message at 7:20 am, following which they started to ask the parents coming to school with their children to return.
"The school administration declared that all the students should be asked to return. Only a few children were already inside the campus and they were also sent back," he told PTI Videos.
AAP supremo Kejriwal, who had on December 9 hit out at the Delhi Police and Union Home Minister Amit Shah over that day's bomb threats, shared a news clip about the latest threats on his official X handle.
"This is the second time this week that Delhi schools have received bomb threats, which is extremely serious and worrying. If this continues, how badly will it affect the children? What will happen to their studies?" he asked in Hindi in the caption of the post.