Sussex Police have issued new pictures of Mackenzie Crook's missing sister-in-law - who missed a chemotherapy session and is considered "very vulnerable".
Laurel Aldridge, 62, from Walberton near Arundel, has not been seen since leaving home on Tuesday morning.
Officers, while pursuing "multiple lines of enquiry", are "concerned" and are urging local residents to check their outbuildings.
Crook, who starred in The Office and Detectorists, has said the family are "really worried" about Ms Aldridge, who he described as a "wonderful mother" and "usually very happy".
The new photographs show her wearing a turquoise fleece, maroon tartan scarf and brown hat. She also had a grey puffer jacket with her.
She is about five foot four, with grey/blonde highlighted hair, and sometimes wears glasses.
"She is considered to be very vulnerable and anyone with information of Laurel's whereabouts is asked to report it to police," the force said in an update.
Detective Sergeant Alan Fenn said he would be grateful if "residents in the Walberton and Slindon areas could check their outbuildings for any sightings of Laurel".
He added: "Also, anyone who was in the Walberton area on Tuesday morning or has video footage of someone matching Laurel's description is asked to report it to us."
The local community is joining in the search, Crook has said. "A lot of people are looking in the local woodlands along the roads and stuff like that," he told ITV.
Describing his sister-in-law's disappearance as "very out of character", he added that she had missed a chemotherapy session on the day she went missing.
"If I could appeal to everyone. Even if they checked before, check again in likely places where she might have crept in to lay down for the night."