FOUR men were arrested after armed officers attended several Bradford addresses.
West Yorkshire Police said it was part of an "ongoing investigation".
One resident said Hollybank Road in Great Horton was shut just before midnight.
They said they also saw a police helicopter in the BD7 area for around half an hour.
The men, aged between 22 and 28, remain in custody.
Full West Yorkshire Police statement
A spokesperson for the force said: "At about 11.30pm yesterday (Wednesday, November 27), police attended addresses in Bradford in connection with an ongoing investigation.
"Due to information received armed officers were deployed as part of the operation.
"Enquiries led to the arrests of four men aged between 22 and 28 in connection with this matter.
"They remain in custody today while enquiries are continuing."
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