A 48-year-old man is the second man seized in connection with the murders of five women found near Ipswich, in the Suffolk countryside.
He is being held on suspicion of murdering prostitutes Gemma Adams, Anneli Alderton, Tania Nicol, Paula Clennell and Annette Nicholls.
The first suspect, Tom Stephens, 37, was arrested on Monday.
The second person, whose name was not communicated, was arrested at his Ipswich home at 0500 GMT. Police activity has been reported at a house in the London Road area of Ipswich.
The house has been cordoned off by police, and forensics officers are in the property.
"This investigation continues to grow," said Brunt. A dark Ford Mondeo was taken away by police.