Rodent sightings in Beacon Hill and the Back Bay have doubled since this time last year, according to Boston Inspectional Services, the city agency responsible for handling pest complaints.,An improvement project aimed at some of Boston’s oldest sewer lines may be leaving residents in nearby neighborhoods with some unwanted furry foes.

Rodent sightings in Beacon Hill and the Back Bay have doubled since this time last year, according to Boston Inspectional Services, the city agency responsible for handling pest complaints.

Twenty-one rodent complaints were filed during September 2006, compared with 10 complaints in September 2005, said Boston’s Principle Health Inspector John Meany.

City officials and residents of the neighborhoods suspect that the increase in complaints is the result of a project to line the century-old sewers in Beacon Hill with fiberglass.

The liners were inserted through manholes on Charles Street between Revere and Beacon streets, and on Beacon Street between Charles and Dartmouth streets.

The project should be completed sometime this week, said Thomas Bagley, a spokesman for the Boston Water and Sewer Commission.

“Did we disturb [the rats]? I would say probably,” Bagley said.

The increase in complaints may also be due to the publicity the project has received rather than an actual increase in rat sightings, Bagley said.

“Someone was talking about rats the size of small children,” said John Boucher, an exterminator at Waltham Pest Control in Burlington, the company hired to control the rodents in the construction area.

Despite the rumors, Boucher said he has not seen an increase in the number of rats in the area.

“The problem in the Beacon Hill area is pretty much minimal,” Boucher said. “The rats did get shot up to the surface, and when they surface, they’re going to scare people.”

Rodent bait containing an anti-coagulant lethal to rats will be placed in the sewers and storm drains in the area every week for the next month.

Boucher recommended beginning rodent control six weeks prior to any project that will disturb the rats’ habitat, he said.

But according to him, the city only had his company bait the area once construction was underway.

Despite this, the extermination effort has already been successful, Boucher said.

“[The rats] cleaned out my bait,” he said.

Some Emerson students living in the area have experienced problems with rodents.

Junior film major Jonathan Marlow spotted a mouse running across the floor of his Beacon Hill apartment last week.

Marlow has lived in his apartment a few blocks east of the construction since the beginning of last month.

When he first heard scurrying noises in his apartment, he didn’t know what to think.

“At first, I thought I was just imagining things,” Marlow said. “But then I saw a mouse run across my bedroom floor. He ran into my closet and ate an entire box of my protein bars.”

Marlow plugged a hole in the floorboard the mouse was using to enter the apartment and hasn’t seen it since.

He said he has not seen any rats in Beacon Hill in the past weeks.

“I thought people were making too big a deal about it,” said junior film production major John McCarthy. “I think the city government is taking the appropriate actions.”

McCarthy has periodically dealt with cockroaches and mice during the one-and-a-half years he has lived in Beacon Hill but says he has never had a problem with rats.

“The rat problem in Beacon Hill is in decline,” said Boucher.

He added that some neighborhoods in Cambridge and Boston’s Fenway district have the city’s worse rodent problems.

“The rat is an animal of harborage,” said Boucher. “It’s just looking for somewhere to live. They like us about as much as we like them.”