Police cordoned off a Middlesbrough pub after gun fire damaged two of its windows.
Cleveland police were called to the Park End pub in the town at around 8.30am following reports of the damage.
A cordon was placed around the premises as investigations continued.
Detective Inspector Matt Murphy-King, said: "Incidents of this nature are rare across Cleveland and we are committed to finding those responsible and bringing them to justice.
"We have forensic and trained search officers conducting an examination of the scene and a team of detectives focussing on the investigation.
"I want to reassure the local community that we are taking this incident extremely seriously and that there will be an increased police presence.
"I would urge anyone with information regarding the incident to contact us, whether they have seen or heard anything and no matter how trivial they may feel the information is. A small piece of information could be key in an investigation such as this."
Anyone with information is asked to contact Middlesbrough CID on the non-emergency number 101 or Crimestoppers anonymously on 0800 555 111.