Police in India have arrested seven people and seized 6.4 kilogrammes of uranium from their possession, Indian media reported on Friday, marking the second time in less than a month that authorities have captured a large quantity of the radioactive material from unauthorised persons in the country.

According to the Indian Express, the incident took place in the eastern state of Jharkhand in Bokaro district. The report said that officials had not yet arrested the prime suspect from whom the substance was procured.

“Seven people were arrested for possessing and planning to sell a mineral, which is suspected to be uranium after we received a tip. We are further investigating the case and the mineral [has been] sent to the lab to check its veracity," the report quoted SP Chandan Jha as saying.

However, the publication noted that the press release issued by the Bokaro police and the FIR mentioned the mineral to be uranium. "SP Jha refused to comment on whether any other investigating agency was involved and also did not comment on whether they sought custodial interrogation of the arrested accused," the publication said.

According to the Times of India, the suspects — suspected to be part of a national gang involved in illegal uranium trade — were searching for customers and had fixed its price at 5 million INR. The report added that two of the men arrested have a criminal history.

"It is unclear how they got their hands on the radioactive material. During interrogation, they mentioned West Bengal, Giridih and a few other places. Seven mobile phones and a motorcycle were also seized from them," the publication quoted the same SP as saying.

Last month, Indian police had seized over seven kilogrammes (15.4 pounds) of natural uranium and arrested two men in the western Maharashtra state for “illegally possessing” the highly radioactive substance.

It was the second time in India that such a highly radioactive substance was seized by police in recent years. In 2016, police seized almost 9kg (19.8 pounds) of depleted uranium in the Thane area of Maharashtra.

Pakistan expresses deep concern

The Foreign Office in Islamabad expressed concern over "yet another incident of attempted illegal sale" of uranium in India.

In a statement, FO Spokesman Zahid Hafeez Chaudhri said the similar incident in Maharashtra last month and other such reports in the past "are a matter of deep concern as they point to lax controls, poor regulatory and enforcement mechanisms, as well as possible existence of a black market for nuclear materials inside India".

The UN Security Council Resolution 1540 and the IAEA Convention on the Physical Protection of Nuclear Material (CPPNM) make it binding on states to ensure stringent measures to prevent nuclear material from falling into wrong hands, the statement noted.

"Pakistan reiterates its call for [a] thorough investigation of such incidents and measures for strengthening the security of nuclear materials to prevent their diversion," it added.

The press release said it was "equally important to ascertain the intent and ultimate use of the attempted uranium sale given its relevance to international peace and security as well as the sanctity of global non-proliferation regime".

Uranium is used in several areas, including nuclear explosives and medical techniques. The very fact that some people stole or illegally mined uranium raises concerns about nuclear safety and security in India. It also indicates the possibility of a nuclear market existing in India that could be connected to international players.

Pakistan had voiced serious concern last month too after reports of the Maharashtra seizure emerged, pointing to gaps in state control mechanisms there.

“We have noted with serious concern the reports about seizure of more than 7kg natural uranium from unauthorised persons in India,” Chaudhri had said at the time.

“Security of nuclear materials should be the top priority for all countries,” he added.

“There is a need for thorough investigation of the matter as to how such sizeable quantity of uranium could become available outside any state control and identify the gaps which made this possible.”