Chief Deputy District Attorney Arnold Mordkin said last week that a grand jury was convened earlier this year in part to consider the deaths of Parker and Caroline Lofgren of Denver and their two children, ages 8 and 10.
The Lofgrens were found dead the day after last Thanksgiving in an Aspen-area home where they were spending the holiday.
Investigators say a disconnected exhaust pipe leaked the odorless gas into the house. The home didn't have a carbon monoxide detector even though a county ordinance required one.
A state law approved this year requires most new homes to install detectors.
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