Cleveland Police are investigating after beach cleaners discovered what could be a grenade at Seaton Carew beach.
Bomb disposal teams from Catterick Garrison are on the way to the scene.
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Police have seized 539 units of alcohol from drinkers as young as 15 in a bid to crack down on underage bingeing.
"Big Sam" was spotted letting his hair down in the seaside resort weeks after securing Premier League survival for Sunderland.