Hundreds of households were left without phone or broadband services after cabling was cut by vandals in Tweedbank.
A manhole was tampered with near Galafoot Bridge and 800 telephone and broadband lines were damaged.
The incident occurred between 00:00 and 02:00 on Wednesday 26 July.
Insp Tony Hodges said: "This is a mindless attack on the community, leaving many people without essential phone lines and internet services.
"We are keen to speak to anyone who may have been in the Kingsknowes Bridge and Tweedbank areas in the early hours of Wednesday 26th and may have seen or heard anything suspicious."
A BT spokesman said the operator was working to repair the damaged lines as quickly as possible and expected to have the service completely restored later on Thursday.