Officers discovered 900 marijuana plants Wednesday concealed inside several units of a warehouse during raids at a Santa Rosa business park, police officials said.

No one was arrested, and officers encountered no tenants as they began searching six units in neighboring warehouses on the 900 block of Piner Road at about 9 a.m., Santa Rosa Police Sgt. Chad Heiser said.

Authorities asked nearby mechanics, lumber dealers and other shops to temporarily lock up before they broke down the doors.

The warehouses are across and down the street from a Piner Place shop where officers pulled 180 plants two months ago from a business called Audio Legends. In that case, the tenant was arrested.

"Marijuana is a very lucrative crop. People are looking for larger areas to grow more plants and make more profit," Heiser said.

Marijuana cultivation has proliferated at business parks in the city, said Heiser, who runs the narcotics unit. As indoor marijuana gardens became prevalent in some residential areas, so did complaints about the skunky smell of pot, increased traffic and other concerns.

"They are getting out of residential areas where there tend to be more complaints," Heiser said. "It is something we're spending more time on this year."

A patrol officer who once worked with the narcotics team started noticing certain kinds of traffic and other signs of cultivation at the Piner Road business park. He started watching the businesses and reported his findings to the narcotics unit, Heiser said.

On Wednesday, about 20 narcotics officers from Santa Rosa, the Sonoma County Sheriff's Office and the U.S. Drug Enforcement Administration searched three units each at 950 and 966 Piner Road.

They found more than 900 plants in various stages of growth, the largest 3 to 4 feet tall, spread among five units, Heiser said.

In both buildings, two of the units had been connected internally with cultivation efforts apparently linked.

A sixth unit was being converted into what appeared to be a typical marijuana nursery but had no plants, Heiser said.

Detectives are still investigating who was involved in the cultivation, Heiser said.

City code enforcement officials found unauthorized construction to create rooms within the buildings and potentially illegal electrical wiring, Heiser said.

A phone call to warehouse management was not immediately returned.

The strong odor of marijuana soaked the business park late Wednesday. But neighboring tenants said the smell wasn't prevalent until the morning raids.

"When they rolled up the door you could really smell it," said Brian Donohue, whose family has run an auto shop in the area for 30 years.

Metal bars secured the doors that law enforcement broke to get inside. An orange "Stop Work Notice" from the city posted on one door warned the tenant to contact the code enforcement bureau.

Beyond the glass doors, several of the units had what appeared to be minimal front offices.

One had no sign and what looked like a GPS unit on a desk next to the water cooler. Through another door, what appeared to be a beer cooler as well as equipment, bags and jugs stood against a large plywood wall.

Around the corner, one front office contained a desk with computer and phone and even had a clock and landscape painting on the wall.

Neighbors said the tenants kept to themselves. One man showed up nearly every day while, in the other building, a man said the male tenant appeared rarely and only at night.

Heiser said the setups inside were similar to the concealed indoor nurseries they found Feb. 21 in the Piner Place warehouse.

On that day, officers searched two units and found what appeared to be a legitimate medical marijuana cooperative in one. The other unit contained about 180 plants and growing systems in three rooms hidden behind the audio business.

One of the entrances to the building was concealed behind a large rolling cabinet.

Officers arrested the tenant, Lance Guyan, 29, of Santa Rosa, on March 4.

Guyan was charged with two counts of marijuana cultivation, marijuana possession for sale and maintaining a place for the manufacture of a controlled substance, Sonoma County Deputy District Attorney Robert Maddock said.

Guyan was released on bail. His next scheduled court appearance is April 26.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.