Chief Minister Himanta Biswa Sarma has said that one more person has been arrested in Assam for putting up social media posts supporting the Delhi blast, taking the total number of such arrests to 21.

He asserted that no person lending support online to terrorists will be spared.

Sharing the update in an X post late on Saturday evening, Sarma said, "Another anti-national has been arrested by @assampolice, taking the total count to 21."

"We will NOT tolerate anyone expressing support online for terrorists behind the Delhi terror attacks," he added.

Among those arrested, three each are from Kamrup and Bongaigaon, two each from Chirang, Lakhimpur and Barpeta, and one each from Darrang, Goalpara, Nalbari, Hailakandi, Hojai, South Salmara, Kokrajhar, Bajali and Dhubri.

As the probe into the "white collar" terror module widens, the police have detained a medical student at the Government Medical College (GMC) in Jammu and Kashmir's Anantnag.

Security agencies are trying to find out whether Priyanka Sharma, a resident of Haryana's Rohtak, had links with the accused doctors.

According to sources, Delhi bomber Umar had rented a house in Haryana's Nuh shortly before the blast near Red Fort.

Investigations have revealed that Umar stayed for around 10 days in a rented room in Hidayat Colony before the blast.

According to police sources, around 1 am on November 10, Umar left this rented accommodation in his i-20 car carrying explosive materials.

It is being said that after failing to withdraw money from an ATM in Firozpur Jhirka, Umar came to Nuh and rented a house here. None of the neighbours got any hint that he was staying in the area, and even the intelligence unit deployed in the district did not receive any information about him.

CCTV cameras installed at an ultrasound centre in Nuh captured Umar's car entering the colony.

An extremely volatile explosive, infamously known as the 'Mother of Satan,' was likely used in the blast that ripped through the heart of the national capital a week ago, investigators suspect.

Triacetone triperoxide (TATP) can explode simply due to heat, without any detonator, officials said, with forensic experts now trying to confirm if it was indeed TATP behind the deadly blast.

SP Vaid, the former Director General of Police (DGP) in Jammu and Kashmir, said on Sunday that the Al Falah University (whose doctors have been arrested in the blast case) looked like a hub of terrorism.

"... I was listening to the media that the owner of this Al-Falah University was in jail for three years for fraud. I don't know how such a person can get a license for a university... It is very unfortunate that such a thing was happening, and I am glad that the government has directed the ED and NIA and other agencies to look into its accounts for any foreign funding...," Vaid told the news agency ANI.

"How can a university function without NAAC accreditation?... I am glad that the government is going after such fraudulent universities... Such a university should be immediately closed...," he added.

The National Investigation Agency (NIA) on Sunday morning started carrying out raids in Delhi, Jammu and Kashmir, Punjab, Haryana, Uttar Pradesh and Madhya Pradesh in connection with Monday's explosion near the Red Fort. 

The white coloured Hyundai i20 used in Monday's explosion near the Red Fort entered the Al Falah University on October 29. The car left the university campus on October 30 at around 2.41 pm

Dr Philipp Ackermann, the German Ambassador to India, said on Sunday that the November 10 explosion near the Red Fort was a shocking event. "We were taken by total surprise. I am extremely saddened to see what happened. My heart goes out to those who lost their loved ones, those who are injured. We have been following everything in the news, and it is a terror attack, obviously..," Dr Ackermann told the news agency ANI. 

Officials investigating the Delhi blast have said that the explosive used doesn't require a detonator and can explode simply from heat. According to experts, TATP (Triacetone Triperoxide) is extremely sensitive- friction, pressure or rising temperature can trigger an explosion.

Officials believe Umar Mohammad was aware of how unstable TATP was before he entered the location where the explosion occurred. 

Umar Mohammad, the driver of the Hyundai i20 car that exploded near the Red Fort earlier this week, allegedly received Rs 20 lakh through illegal financial channels as funding, investigations into the terror attack that claimed 13 lives so far have revealed.

Delhi Police sources told NDTV on Sunday that three 9mm caliber cartridges were recovered from the explosion site. Two of these were live cartridges while the third one was an empty shell. It is important to note that 9mm pistols are not allowed to be owned by ordinary people. 

Nearly a week after the explosion near the Red Fort, all gates of the Red Fort Metro Station have been reopened for the public.