Fourteen people have been arrested in a multi-agency operation to rescue the Italian student volunteer who was abducted by gunmen in Chakama, Kilifi County.
The attackers kidnapped Silvia Constanca Romano and wounded five locals on Tuesday night.
Ms Romano, 23, a manager of a non-governmental organisation known as African Milele Onlus, had been staying in a house in the village.
She had gone to pick a power bank when the gunmen attacked.
Police sources in Malindi said 14 people were apprehended during a Wednesday night operation in Chakama and Galana-Kulalu and that they were taken to various police stations for interrogation.
Coast regional police commander Noah Mwivanda said the two motorbikes are believed to have been used by the attackers and the security agencies had extended the search to Tana River and Taita Taveta counties.
Police are hunting for Mr Said Abdi Adan, a resident of Tana River, who is said to have escaped from the area a few days before the abduction.
A local, Mr Malik Said Gasambi, told journalists that Mr Adan rented a house at Chakama and later brought two people to live there.
“I gave them two rooms in which they spent nights chewing miraa,” he said. "Surprisingly, all of them have been missing since the attack. They silently left with everything that was in the house."
On Wednesday, Kilifi County Commander Fredrick Ochieng’ rescued three people, who had travelled to Chakama, from lynching by a mob on claims of associating with the assailants.
Residents protested against increasing cases of insecurity when Deputy Governor Gideon Saburi, Magarini member of parliament Michael Kingi and Adu Ward Representative Stanley Kenga toured the area.
The leaders' efforts to calm the people were futile. They hurled stones at pastoralist members of the Somali and Oromo communities when alighted from a bus in Chakama and threatened to attack them with stones, clubs and machetes.
Police rushed those who got injured to Malindi Sub-county Hospital.
The residents said they were afraid because of the possibility of retaliation by the pastoralists.