More must be done to raise awareness of the dangerous effects of laughing gas, councils have warned.
The Local Government Association (LGA) said it was "deeply disturbed" that nitrous oxide - which can result in a loss of blood pressure, fainting and even heart attacks - is still viewed as a safe legal high.
On a single Saturday night, one London council confiscated more than 1,200 canisters of laughing gas, while other local authorities are seizing "hauls" of the chemical, according to the Local Government Association.
Hackney Council in east London said that it took the small metal containers outside the pubs and clubs in Shoreditch on a Saturday night last month.
Officials in Norfolk, Hertfordshire and Thames Valley have reported increasing numbers of cannisters being found.
Political parties across the country suspended their General Election campaigns following the Manchester Arena terror attack on Monday.
Investigators believe Mr Kushner has significant information relevant to their inquiry, officials told NBC News.
The men were detained as part of an investigation by MI5 and the Metropolitan Police's Counter Terrorism Command.