A police helicopter and police dogs were called to reports of people trying to throw drugs into a prison near Haverhill.
Officers were called to reports of the suspects at HM Highpoint in Stradishall.
In a tweet, Haverhill police said: "Just finished some foot patrol of the Haverhill Car Boot Sale when we got reports of suspects trying to throw drugs into HM Highpoint.
"Attended and with the help of the National Police Air Service and Norfolk and Suffolk Police Dogs two males were detained and multiple packages seized."
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