You've noticed cars show up at all hours of the day and night, the curtains are always drawn and strange smells are known to waft from the windows every now and again.
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The new neighbours were popular, disliked natural light and didn't know how to cook, you told yourself.
Or could there be something more sinister at play?
Police have urged Canberrans to be on the lookout for illicit drug manufacturers and criminals who cultivate cannabis in their neighbourhoods, and to report any suspicious activity.
It comes after officers seized 2.5 tonnes of precursor chemicals, which they believe were used to make illicit drugs including ecstasy, from a commercial-grade drug lab in Hume last Tuesday.
It was the only major drug lab ACT police have raided in the past year, however they have uncovered eight illegal cannabis grow houses in that period.
Police found crops under cultivation at two homes within a week in Ainslie last month.
One rental property contained 23 cannabis plants and a hydroponic set up.
A house fire, believed to have been sparked by a hydroponic set up inside, led police to 32 cannabis plants at a Hawdon Street property just a few days later.
ACT Policing North District Superintendent Brett Kidner said the heat generated by grow houses, as well as the electrical loads involved, meant homeowners and neighbours were exposed to a high fire risk.
So what should you be on the lookout for?
Clandestine drug labs
Hidden drug labs were often used to manufacture hard drugs such as methamphetamine, heroin and pseudoephedrine, an ACT Policing spokesman said.
Warning signs included persistent chemical smells, suspicious run-off in nearby drains and pool-cleaning equipment around a house or premises which didn't have a pool.
There might also be excessive chemical containers, or empty containers which could have contained chemicals, fertiliser or pills in the rubbish.
Premises used to manufacture drugs often contained volatile and toxic chemicals.
These buildings might have drawn curtains and windows which were shielded during the day, as well as extensive security systems.
There could be frequent visitors who only stayed for a short time, or people seen to carry laboratory equipment into the premises.
A large amount of empty chemical fertiliser, acidic or alkaline containers lying around could also be a sign of drug manufacture.
Cannabis grow houses
Police said criminals could cultivate cannabis inside a house, shed or backyard. Hydroponic set ups for large crops were often very sophisticated and involved a lot of equipment.
They advised neighbours to keep an eye out for people who arrived at a house at odd hours, such as very early in the morning or late at night.
They could also see tradespeople who arrived at the house with items such as large circuit boards, electrical cables, insulation batts or heavy plastic sheeting.
Residents who neglected their garden, did not collect their mail or never put their garbage bins out might also be a warning sign.
Suspicious equipment could include electrical transformers, lights and shades, large quantities of plastic pots or tubs, irrigation piping and large quantities of fertiliser.
Neighbours could also notice lights that switched on and off even though it appeared no-one was at the house, strange interior lighting or the constant sound of fans or water running.
The smell of cannabis was also a giveaway.
Detective Sergeant Shane Scott said residents played a key role in reporting suspicious activity to police, and he encouraged residents to get to know their neighbours.
"If there is a lack of occupancy in the home, the occupants remain very secretive or people frequent the premise intermittently, these may be signs that the house is being used for something other than a home."
"By keeping an eye out, neighbours can assist police in detecting these properties and getting drugs off our streets."
Police said anyone who noticed suspicious activity should take note of time and location, the person’s clothing and appearance and the model, make, colour and registration of any vehicles.
Suspicious or illegal activity can be anonymously reported to Crime Stoppers on 1800 333 000.