Officers believe a man who was found in the street with a fractured skull was assaulted.
Police in Morecambe are now appealing for witnesses after a 45-year-old was found in Albert Road, in the town, on Tuesday.
It is thought the man was attacked, leaving him with a fractured skull and a bleed on the brain.
He was taken to Royal Lancaster Infirmary where he remains.
Officers are asking anyone who saw or knows what happened to get in contact.
DC Peter Bennett from Lancaster CID said: “We are looking at how and why the victim has come to be seriously injured and need anyone who witnessed the attack or who may have CCTV footage of it to speak to us.
“If you saw anything or anyone acting suspicious in the area at the time, please call us on 101 quoting incident reference 1591 of March 3 or email 3786@lancashire.police.uk.”
Alternatively, you can contact independent charity Crimestoppers on 0800 555111 or online at crimestoppers-uk.org.
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