The woman, 54, was taken to hospital, where her condition was stabilised.
Advocates of Israeli settlement policies say the industrial zones are an example of the benefits Palestinians have under Israeli control, including much-needed employment to Palestinians.
Soldiers, as well as police and Shin Bet internal security officers "operated in the village of Shuweika, north of Tulkarm, from which the terrorist originated", the military said.
But other workers in the industrial zone suggested the attack was carried out by a disgruntled employee and was not politically motivated.
The 23-year-old Palestinian used a homemade gun, known locally as a "Carlo", according to Conricus, in the apparent "lone-wolf attack". "We know he is still armed and considered risky", he added. Closed-circuit footage from the scene showed a man holding a handgun and wearing a backpack, fleeing down a flight of stairs and then dashing past stunned onlookers.
Security forces were searching for the suspected perpetrator, Conricus said.
Naalwa was employed at the same plant in the northern West Bank site as his two victims - Kim Levengrond Yehezkel, 28, and Ziv Hagbi, 34.
At his weekly Cabinet meeting, Netanyahu said they had been killed "with great cruelty. I was very surprised by what happened; there was no sign he was planning such a thing", he was quoted by the paper as saying.
Gaza's Hamas rulers and other militant groups praised Sunday's attack, but none claimed responsibility for it.
"No way in our industrial zone", he said, describing an atmosphere of camaraderie in Barkan".
Some Israeli media reported the Palestinian suspect had been recently fired from his job at the site, raising speculation the attack may have been motivated by a personal vendetta.