Schools, railway stations and airports this year have been subject to hundreds of bomb threats, which have later turned out to be hoaxes.
olice in India's capital Delhi have searched around 40 schools after they received anonymous bomb threats, a police spokesperson has told the BBC.
The schools received emails threatening that bombs would be detonated unless $30,000 (£23,582) was paid to the sender, news agency ANI reported.
No bombs have been found yet, but police have not confirmed if the threats are fake.
Hoax bomb threats have often led to chaos at schools, railway stations and airports in India, especially this year.
India's airlines and airports received nearly 1,000 hoax bomb threats this year as of 14 November, causing long delays and flight diversions. It's still not clear what sparked the dramatic surge this year compared with previous years.
In May, thousands of students were evacuated from nearly 100 schools in and around Delhi after fake bomb threats were emailed to them.
On Monday, videos showed parents picking up their children from schools in the morning.
"This is the second time this year that something like this has happened. It is wrong and affects our child's education," a parent picking up his child told news agency IANS.
According to ANI, two of the schools received the emails on Sunday night and the others on Monday morning.
A spokesperson for the Delhi Police told local media that they were working to trace the origin of the email and identify the sender.
Delhi Chief Minister Atishi (she uses only one name) has accused the federal government - led by Prime Minister Narendra Modi's Bharatiya Janata Party (BJP) - of failing to ensure the safety of residents.
"After daily incidents of ransom, murders, and shootings in Delhi, now we are receiving threats of school bombings," she wrote on X.
The Delhi government is run by the Aam Aadmi Party (AAP), but the police report to the federal home ministry. The federally appointed lieutenant governor, the constitutional head of Delhi, has not commented on the bomb threats yet.
Airlines and airports in India received 999 hoax bomb threats from the start of the year until mid-November, and 12 people had been arrested during the same period, government data shows.
Two schools got the threatening email on Sunday night, which said multiple bombs were planted inside buildings and would be detonated if the sender was not paid $30,000, according to news agency.
Many other schools received the emails on Monday morning, prompting school authorities to call parents to take the students home for the day.
Parents were seen picking their children up from the gates of some schools as police checked school premises for suspicious items.
Police officials in Delhi did not immediately respond to a request for comment from Reuters.
In May, more than 50 schools in Delhi and the adjoining suburb of Noida received similar bomb threat emails that turned out to be hoaxes.
