It follows a report that an object was thrown into a car at  Innisfree Gardens in the town.
The incident was reported to police at about 08:15 BST on Wednesday.
A number of houses have been evacuated.

Mustafa Bashir, 34, also forced bleach into her mouth, but the judge in Manchester said his sentence took into account his wife was not "vulnerable".
Both Jess Phillips, Labour, and Maria Miller, Conservative, said they were concerned by the case and would write to the attorney general.
Bashir's ex-wife said she was "disappointed" by the judge's comments.
At Manchester Crown Court, Bashir of Hebers Court, Middleton, Manchester, admitted two counts of assault occasioning actual bodily harm.
Judge Richard Mansell said his decision on the sentence was guided by the fact he was "not convinced [Bashir's then wife] was a vulnerable person" as she was "an intelligent woman with a network of friends" and a degree.
Despite acknowledging the attacks had an "ongoing effect" on his victim's ability to trust people, he sentenced Bashir, who played cricket for Oldham, to 18 months, suspended for two years.
Speaking to the BBC, which has agreed not to use her name, Bashir's ex-wife said she was "disappointed in the comments which the judge made about my vulnerability".
She added: "I am a confident and strong woman because of what I have suffered. I was suffering for my life but the judge didn't believe me."
The judge also ordered Bashir to attend a workshop entitled ''building better relationships'', pay Â£1,000 costs and banned him from contacting his ex-wife indefinitely.
Ms Phillips, who is MP for Birmingham Yardley, said the judge's comments sent a "dangerous" message.
"Your vulnerability and your risk is a completely dynamic thing," she said.
"Everybody has a dynamic risk, I've met women who went on to be murdered who had law degrees, who were very eminent business people.
"There's no category that domestic violence does not touch. It does not follow class lines, it does not follow race lines, it does not follow age lines."
Ms Miller, chair of the Women and Equalities Select Committee, told the BBC: "The brutality of the sort of acts that have been outlined really make me believe that this was a devastating episode in the victim's life.
"I do think this needs to be properly understood by judges and it needs to be properly accounted for in sentencing."
An apparent defence claim, noted by the judge, that a prison sentence would have lost Bashir a contract with Leicestershire County Cricket Club (LCCC) has been rejected by the club, which denies it has ever been in contact with Bashir.
The CPS said: "We are aware of recent developments relating to this case and are currently considering our options."
Anna Soubry, Conservative MP Broxtowe in Nottinghamshire, said: "Police need to get a statement from LCCC.
"They may want to consider whether any other charge needs to be brought if the defendant has deliberately advanced something that is not true to reduce the sentence and/or keep him out of prison."
While the offence is not one where the sentence can be referred to the Court of Appeal as "unduly lenient", the judge has 56 days to recall it if doubt is cast on the grounds for the sentence.
Army bomb disposal experts have been sent to the scene of an alert in Strabane, County Tyrone.
[NEXT_CONCEPT]
MPs have criticised a judge over a suspended jail term given to a man who attacked his wife with a cricket bat.