Negotiators have been talking to the man through a 4in-wide (10cm) ventilation pipe.

BBC: Alabama hostage standoff for five-year-old continues

Authorities have been conferring in a nearby church and communicating with Dykes through a ventilation pipe to the underground bunker.

NPR: Ala. Town Mourns For Bus Driver Amid Standoff

During the six-day standoff, officials talked to Dykes and delivered medication and toys to the boy through a 4in (10cm) ventilation pipe.

BBC: Alabama kidnapper dead and boy saved after police raid

During the six-day standoff, negotiators talked to Dykes and delivered medication and toys to the boy through a 4in (10cm) ventilation pipe.

BBC: Alabama hostage-taker died 'in firefight'

Negotiations are being carried out between the suspect and authorities through a 60-foot plastic ventilation pipe that leads from the bunker, authorities said.

CNN: Amid standoff, Alabama town mourns slain bus driver

As it turned out, authorities' decision to rely on every tool at their disposal was a wise one: Dykes had planted an explosive device in a ventilation pipe he'd told negotiators to use to communicate with him on his property in the rural Alabama community of Midland City, and also placed another explosive device inside the bunker, the FBI said in a statement late Tuesday.

WSJ: Military tactics, arms, helped rescue Ala. hostage