Twenty people have been detained over the abduction of an Italian woman from a village in southeast Kenya, the east African country's police chief said on Friday.
An armed gang seized Silvia Romano, a volunteer with a charity, on Tuesday in Chakama, 60 kilometres inland from the coastal town of Malindi, an area popular with Italian tourists and expatriates.
The 23-year-old's whereabouts are unknown.
"We have 17 people in custody. We have further arrested three other persons whom we consider as persons of interest to this investigation," Inspector General Joseph Boinett told reporters on Friday.
"They have given us very valuable information which has gone to assist the ongoing operation to trace and rescue the lady who was abducted by unknown persons," he added.
The gang shot and wounded five people, including three children, while abducting Romano and escaped across the nearby Galana river.
A police manhunt has so far failed to find any trace of the kidnappers or Romano, who was volunteering for Italian charity Africa Milele Onlus.
Police are considering motives, including robbery, but some fear Romano could be smuggled north towards the Somalia border, where other abductees have been taken in the past.
A spate of abductions on the coast in 2011 saw a British man shot dead and his wife, Judith Tebbutt, kidnapped from a resort island.
Weeks later a French woman, Marie Dedieu, was abducted from her home on Manda island in the Lamu archipelago.
Both women ended up in Somalia, where Tebbutt was released after six months, while Dedieu died of ill health.
Gunmen from the Al Qaeda affiliated Shabaab militant group also abducted two Spanish aid workers in 2011 from the Dadaab refugee camp close to the Somali border.
"We have significant measure of optimism that we should be able to find the lady within the shortest time possible," said Boinett, discussing Romano's case.